[postgis-users] Spatial linking or selection

[Nicolas Ribot]

On Fri, 15 May 2020 at 12:56, Shaozhong SHI <shishaozhong at gmail.com> wrote:

> Hi, Nicolas,
>
> Thanks.
>
> That is very interesting.  I will test it.
>
> I could not find information on how distance is defined.  0.01 stands on
> what unit?
>
>
In the unit of your spatial reference system (see its wkt or proj4
definition in spatial_ref_sys table to figure out the SRS unit)

https://postgis.net/docs/ST_DWithin.html
>
> Regards,
>
> Shao
>
> On Fri, 15 May 2020 at 11:32, Nicolas Ribot <nicolas.ribot at gmail.com>
> wrote:
>
>> Hi,
>>
>> You can test for proximity between start and end points
>> Create spatial indexes on st_startpoint(geom) and st_endpoint(geom) on
>> your line features table (also index starting and ending points column in
>> table one)
>>
>> select t.id, r.id, r.geom
>> from start_end_table t join roads r on st_dwithin(t.startpoint,
>> st_startpoint(r.geom), 0.01) and st_dwithin(t.endpoint,
>> st_endpoint(r.geom), 0.01)
>>
>> Adjust the 0.01 distance according to your data and their precision.
>>
>> Nicolas
>>
>> On Fri, 15 May 2020 at 11:42, Shaozhong SHI <shishaozhong at gmail.com>
>> wrote:
>>
>>> Given 2 tables.  One has the starting and ending points of roads, and
>>> the other has line features.  How best to do spatial linking or selection
>>> of road features?
>>>
>>> Can anyone enlighten me?
>>>
>>> Regards,
>>>
>>> Shao
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>>
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